The introduction of copper (Cu) metal into multilayer metallization schemes for manufacturing integrated circuits, can necessitate the use of diffusion barriers/liners to promote adhesion and growth of the Cu layers, and to prevent diffusion of Cu into the dielectric materials. Barriers/liners that are deposited onto dielectric materials can include refractive materials such as tungsten (W), molybdenum (Mo), and tantalum (Ta), that are non-reactive and immiscible with Cu and can offer low electrical resistivity. Current integration schemes that integrate Cu metallization and dielectric materials can require barrier/liner deposition processes at substrate temperatures between about 400° C. and about 500° C., or lower.
W layers can be formed by thermally decomposing a tungsten-containing precursor, e.g., a tungsten-carbonyl precursor, in a thermal chemical vapor deposition (TCVD) process. Material properties of W layers that are deposited by thermal decomposition of metal-carbonyl precursors (e.g., W(CO)6), can deteriorate when the substrate deposition temperature is lowered to below about 500° C. Increase in the (electrical) resisitivity of the W layers and poor surface morphology (e.g., formation of nodules) at low deposition temperatures, has been attributed to increased incorporation of CO reaction by-products into the thermally deposited W layers. Both effects can be explained by a reduced CO desorption rate from the thermal decomposition of the tungsten-carbonyl precursor at substrate temperatures below about 500° C.